1. Field of the Invention
The present invention relates to a printing apparatus which prints predetermined images or letters by forming dots on a print medium by ejecting liquid from a plurality of nozzles.
2. Description of the Related Art
With the wide spread of personal computers and digital cameras, ink-jet printers which are one kind of printing apparatus have been widely used by general users as well as office workers thanks to the advantage that they enable high quality color print copies to be attained at low cost.
Such an ink-jet printer forms fine dots on a print medium by ejecting (discharging) liquid-state ink droplets from nozzles of an ink-jet head while moving the print medium and the liquid ejecting head (also called ink-jet head) in relative to each other, and thus produces a desired print copy by forming predetermined letters or images on the print medium. A printer in which an ink-jet head is loaded on a moving unit called a carriage which is to move in a direction which intersects a transporting direction of the print medium is generally called a multi-pass ink-jet printer. On the other head, an ink-jet head (which is not necessarily an integrally-formed body) which is relatively long in a direction which intersects the transporting direction of the print medium and which can complete a print by only a single pass is called “line head-type ink-jet printer”.
In such an ink-jet printer, sometimes ink droplets are not properly discharged from nozzles for some reasons; for example bubbles may invade into the nozzles, paper powder or ink crude may stick to the nozzles, ink in the nozzles may dry and a viscosity of the ink may increase. In such cases, ink in the nozzles must be sucked in by reducing the pressure inside the cap while a cap of a cleaning unit is in close contact with a nozzle-formed surface of the ink-jet head. In such a way, nozzles are recovered to be in a normal state. In an ink-jet printer disclosed in JP-A-2005-96116, nozzles are recovered to a normal state in a manner such that caps of cleaning units are simultaneously brought into close contact with the nozzle-formed surface of a line head ink-jet head which is long in a direction which intersects the transporting direction of the print medium and ink in the nozzles is sucked in. Further, a technique in which the nozzle-formed surface of the ink-jet head is wiped by a thin plate member made of rubber called wiper so that meniscus of the nozzles is regulated, and ink or paper powder attached the nozzle-formed surface is removed so that the nozzle-formed surface is recovered to a normal state is familiar.    [Patent Document 1] JP-A-2005-96116